<?php
    class Test
    {
        private $foo;

        public function __construct($foo)
        {
            $this->foo = $foo;
        }

        private function bar()
        {
            echo 'Accessed the private method.';
        }

        public function baz(Test $other)
        {
            // we can change the private property:
            $other->foo = 'hello';
            var_dump($other->foo);

            // we can also call the privet method:
            $other->bar();
        }
    }

    $test = new Test('test');
    $test->baz(new Test('other'));
?>